The present invention relates to floating dry docks and particularly to an improved floating dry dock for small craft including personal watercraft.
In the past floating dry docks have been created by the assembly of a number of identical floating subunits. These units have been roughly cubical with tabs projecting from the vertical edges at or near the horizontal midline. By fastening adjacent tabs to each other, a floating dock with a substantially flat deck surface of any desired configuration could be assembled.
Examples of such units and docks assembled from such units are found in U.S. Pat. Nos. 3,824,664 and 4,604,962. These patents describe hollow cubical units which in practice have been manufactured about 16 inches on a side. The units have been molded from a suitable plastic material with the tabs which project from each vertical edge positioned so that a dock of virtually any shape with a flat deck or top surface could be formed. The units have also been provided with bungholes so that the units could be partially flooded to lower the water line of some or all of the units. This has been done particularly where the dock has been used for personal watercraft.
With a personal watercraft, such as a jet ski, or with other small craft, such as a motor boat or jet boat under about 18 feet in length, the goal of the floating dry dock has been to make it possible to drive the craft up onto the dock. This would enable the driver to get on and off the craft without getting in the water and would also permit the craft to be stored out of the water.
Attempts to accomplish these goals have not been entirely successful. The dry docks assembled from prior art units have been either too high above the water to permit a personal watercraft to be driven on, or too low to keep the driver and craft out of the water entirely. Keeping the craft high and dry when not in use is important to protecting the machinery of the craft. In addition, the surfaces of the dock which the craft slides over must be ordinarily above the water line, otherwise marine growths, such as barnacles, will develop and: scratch the smooth bottom surface to the craft, doing damage each time the craft slides onto or off of the dock.
The prior art has also included floating units like those shown in the patents identified above, but shorter. These units were about 16 inches square in plan view, but only about 10 inches tall. In addition, in these shorter units the tabs were still about 8 inches down from the deck surface and correspondingly closer to the bottom surface. These shorter units have been thought useful for assembling: docks for light watercraft such as the shells used by college crew teams.
The present invention provides a unique floating drive-on dry dock for personal watercraft or small craft under about 18 feet in length. The dock is assembled from a combination of tall and short hollow, air-tight floatation units. The tall units are roughly cubical and have tabs projecting from about midway along each vertical edge. The short units which have tabs positioned to make a deck continuous with the deck formed by the tall units and which are able to flex downward when a craft is driven onto the dock but which resist flexion in the opposite direction when the craft is in place, to thereby form a rigid, stable surface that can be walked on.
Accordingly, the present invention provides a floating drive-on dry dock formed from a plurality of float units each with a generally flat top or deck surface, the float units being connected together so that their top surfaces form a generally planar and horizontal deck. Each float unit has at least one side wall which faces an opposing side wall on an adjacent float unit. The float units each have a pivotable connection to the adjacent float units, the connections being above the water line when the dock is floating freely and a fixed distance below the deck surface of the float unit. The connections enable adjacent float units to rotate with respect to each other until the respective facing side walls come into contact with each other. A first group of the float units have bottom surfaces located substantially as far below the pivotable connection as their deck surfaces are above the pivotable connection whereby they can rotate downward to the same extent that they can rotate upward: before the respective facing side walls come into contact with each other. A second group of float units have bottom surfaces located substantially closer to the pivotable connection whereby they can rotate downward substantially without limitation. The floating drive-on dry dock has a pair of parallel arms formed at least in part of float units from the second group of float units, and there is a bridging unit between the parallel arms, the; bridging unit having a top surface which is above the water surface when the dock is floating freely.
The floating drive-on dry dock so constructed has surfaces on which the watercraft slides which are submerged only while the watercraft is being ridden onto the dock, but which remain above the surface both before and after the craft is driven onto the dock. The result is a dock that does not accumulate barnacles or other harmful marine growth. Moreover, the ability of the short units to permit flexion in one direction but not in the other permits them to flex downward while a watercraft is being driven onto the dock and to form a rigid deck once the craft is in place.